Laser-Induced Dissociation of an Energetic Polymer: A Spectroscopic Study of the Gaseous Products

Previous studies of GAP (glycidyl azido polymer) laser-induced decomposition (Propellants, ExplosiVes, Pyrotechnics 1996, 21, 258), revealed that the shock wave produced from a diluted polymer is more energetic than from the neat polymer. In this paper, direct measurement of the energy disposal into molecular products is reported using spectroscopic methods. Chemiluminescence probes electronically excited species, and laserinduced fluorescence, ground-state radicals. It is found that the initial velocity and internal energy content of small diatomic molecules is larger in some diluted polymers than in the neat one. This finding is in line with a simple model based on the assumption of a self-sustained reaction following initial laser excitation

Multifaceted open social learner modelling

Open social learner modelling (OSLM) approaches are promoted in order to assist learners in self-directed and self-determined learning in a social context. Still, most approaches only focus on visualising learners’ performance, or providing complex tools for social navigation. Our proposal, additionally, emphasises the importance of visualising both learners’ performance and their contribution to a learning community. We seek also to seamlessly integrate OSLM with learning contents, in order for the multifaceted OSLM’s prospect for ubiquity and context-awareness to enrich the adaptive potential of social e-learning systems. This paper thus presents the design of multifaceted OSLM by introducing novel, personalised social interaction features into Topolor, a social personalised adaptive e-learning environment. The umbrella target is to create and study aspects of open social learner models. An experimental study is conducted to analyse the impact of the newly introduced features. The results are finally concluded to suggest future research and further improvements

Angular redistribution of near-infrared emission from quantum dots in 3D photonic crystals

We study the angle-resolved spontaneous emission of near-infrared light sources in 3D photonic crystals over a wavelength range from 1200 to 1550 nm. To this end PbSe quantum dots are used as light sources inside titania inverse opal photonic crystals. Strong deviations from the Lambertian emission profile are observed. An attenuation of 60 % is observed in the angle dependent radiant flux emitted from the samples due to photonic stop bands. At angles that correspond to the edges of the stop band the emitted flux is increased by up to 34 %. This increase is explained by the redistribution of Bragg-diffracted light over the available escape angles. The results are quantitatively explained by an expanded escape-function model. This model is based on diffusion theory and adapted to photonic crystals using band structure calculations. Our results are the first angular redistributions and escape functions measured at near-infrared, including telecom, wavelengths. In addition, this is the first time for this model to be applied to describe emission from samples that are optically thick for the excitation light and relatively thin for the photoluminesence light.Comment: 24 pages, 8 figures (current format = single column, double spaced

Researching the use of force: The background to the international project

This article provides the background to an international project on use of force by the police that was carried out in eight countries. Force is often considered to be the defining characteristic of policing and much research has been conducted on the determinants, prevalence and control of the use of force, particularly in the United States. However, little work has looked at police officers’ own views on the use of force, in particular the way in which they justify it. Using a hypothetical encounter developed for this project, researchers in each country conducted focus groups with police officers in which they were encouraged to talk about the use of force. The results show interesting similarities and differences across countries and demonstrate the value of using this kind of research focus and methodology

Towards ‘Onlife’ Education. How Technology is Forcing Us to Rethink Pedagogy

[EN] The objective of this chapter is twofold: on the one hand, to provide an explanation for the need we have today to rethink pedagogy based on new realities and the scenarios in which we live, also in education, generated by the technology of our time and, on the other hand, to point out the direction in which we can find a path that leads us to that reflection in the face of the inevitable convergence between technology and pedagogy in which we are today

Triggering of the dsRNA Sensors TLR3, MDA5, and RIG-I Induces CD55 Expression in Synovial Fibroblasts

Background: CD55 (decay-accelerating factor) is a complement-regulatory protein highly expressed on fibroblast-like synoviocytes (FLS). CD55 is also a ligand for CD97, an adhesion-type G protein-coupled receptor abundantly present on leukocytes. Little is known regarding the regulation of CD55 expression in FLS. Methods: FLS isolated from arthritis patients were stimulated with pro-inflammatory cytokines and Toll-like receptor (TLR) ligands. Transfection with polyinosinic-polycytidylic acid (poly(I:C)) and 5'-triphosphate RNA were used to activate the cytoplasmic double-stranded (ds)RNA sensors melanoma differentiation-associated gene 5 (MDA5) and retinoic acid-inducible gene-I (RIG-I). CD55 expression, cell viability, and binding of CD97-loaded beads were quantified by flow cytometry. Results: CD55 was expressed at equal levels on FLS isolated from patients with rheumatoid arthritis (RA), osteoarthritis, psoriatic arthritis and spondyloarthritis. CD55 expression in RA FLS was significantly induced by IL-1 beta and especially by the TLR3 ligand poly(I:C). Activation of MDA5 and RIG-I also enhanced CD55 expression. Notably, activation of MDA5 dose-dependently induced cell death, while triggering of TLR3 or RIG-I had a minor effect on viability. Upregulation of CD55 enhanced the binding capacity of FLS to CD97-loaded beads, which could be blocked by antibodies against CD55. Conclusions: Activation of dsRNA sensors enhances the expression of CD55 in cultured FLS, which increases the binding to CD97. Our findings suggest that dsRNA promotes the interaction between FLS and CD97-expressing leukocyte

Controlling waves in space and time for imaging and focusing in complex media

In complex media such as white paint and biological tissue, light encounters nanoscale refractive-index inhomogeneities that cause multiple scattering. Such scattering is usually seen as an impediment to focusing and imaging. However, scientists have recently used strongly scattering materials to focus, shape and compress waves by controlling the many degrees of freedom in the incident waves. This was first demonstrated in the acoustic and microwave domains using time reversal, and is now being performed in the optical realm using spatial light modulators to address the many thousands of spatial degrees of freedom of light. This approach is being used to investigate phenomena such as optical super-resolution and the time reversal of light, thus opening many new avenues for imaging and focusing in turbid medi